Temperature-compensating device.



W. H. BR1STOL.

TEMPERATURE COMPENSATING DEVICE.

APPLICATION FILED JULY 28,1010. 1,000,146, Patented Aug. 8, 1911.

W. my

N u m WILLIAM H. BRISTOL, OF WATERIBIIRY, CONNECTICUT.

TEMPERATURE-COMPENSATING DEVICE.

Specification of Letters Patent.

Application filed July 28,1910. Serial 1%. 574.260.

To all whom it may concern:

' Be it known that I, WILLIAM H. BRISTOL, a citizen of the United States and a resident of Waterbury, in the county of New Haven and State of Connecticut, have invented certain new and useful Improvements in Temperature-Compensating Devices, of which the following is a specification.

The invention relates to a temperature compensating device particularly adapted to sensitive electrical instruments and electrical temperature measuring devices whose indications are affected by small variations of temperature of the medium in which they are placed.

It has for its particular object a compensating device of this character which shall be simple and inexpensive and of substantial construction.

It has for its further object to provide means for varying the initial resistance of said device.

The nature of my invention will be best understood when described in connection with the accompanying drawings, which show the improved compensator specifically applied to the compensation for variations of temperature as afiecting a temperature measuring device employing a thermo electric couple, and in which Figure 1 is a diagrammatic view' illustrating the arrangement of the various apparatus. Fig. 2 is a longitudinal section on an enlarged scale of the compensating dev1ce.

In my prior U. S. Patents No. 783,503 and No. 800,792, I have shown and described means for compensating for the variations of temperature; and in'Patent No. 783,503 particularly for variations of the temperature at the cold end of a thermo electric couple. While the means therein disclosed operate quite satisfactorily, yet their fragility and the'care necessar in construction and the troublesome calibration render the same somewhat unsuitable for commercial purposes. To overcome these objections I have devised the improved device forming the subject of the present invention. As shown in Fig. 2, this device 10 consists essentially of an insulating tube 11 of refractory material such as clay, porcelain or fiber tube, and whose coeificient of ex ansion is low. This tube is provided wit perforations 12 and is threaded at both ends to receive metallic or other suitable material.

caps 13 of brass, iron or the like. These caps are adjustable upon said tube by simply turning the same and are held in any predetermined position by means of lock nuts 14 or the like. Suitable binding posts 15 are also provided thereon for the purpose of inserting the compensator in circuit. Within this tube 11 and held in position by the pressure exerted between the two caps 13 are a plurality of adjacent contact disks 16 and atube 17 with closed ends, or a rod, abutting the same. These contact disks 16 are composed of material having a different coeflicient of expansion from the tube and caps, and may consist of carbon, graphite The tube or rod 17 is preferably of some material having a high coeflicient of expansion, such for example, as zinc, so that with the construction herein set forth a rise in temperature will cause a diflerential expansion to take'place between the graphite disks and the zinc rod on the one hand and the surrounding tube and caps on-the other, the expansion of the former being greater than that of the latter. This diflerentlal expansion will thus cause an increase of pressure between the various contacts and thereby reduce the resistance of the same; and a drop in temperature will correspondingly cause an increase in resistance. The initial resistance is readily adjusted by turning one or both of the caps 13. The tube 17 might of course be omitted and the adjacent disks used throughout the entire length of the tube, but I prefer to employ the said tube 17 of a high coeflicient of expansion, for the purpose of rendering the device more sensitive to temperature variations.

In employing the device 10 in connection with thermo-electric couples, for the purpose of compensating for variations of temperature at the'cold end of said couple, the same is inserted in series with the couple 20, Fig. 1, and in close proximity to its cold end 21. The compensating device 10, belng thus in the medium surrounding the said cold end 21, it will be affected by variations in the temperature of the same, the med um circulating freely through the perforations 12 of the tube 11 and through the tube itself, thus causing the differential ex ansion hereinbefore described to take p ace. As an increase in temperature at the cold end 21 of the couple 20 will cause a decrease of the true indication of the same, it is essential Patented Aug. 8, 1911.

acts to reduce the resistance of the circuit This is efas the temperature increases. fected by introducing the compensating device 10 in series, as explained. The indieating instrument 22, to which 'the couple 20 is connected by means of suitable leads 23, may also be compensated by the herein disclosed device 10, where an increase in temperature causes a decreased reading of the same. For this purpose the said compensating device 10 is inserted in series in the circuit in close proximity to the said indieating or recording device 22, and is thereby subject to the temperature variations in the medium surrounding the said indicating or recording device.

The compensating device herein disclosed is applicable to the compensation of various electrical instruments whose indications are afiected negatively by an increase in temperature of the medium in which they are placed; although the same may readily be made to operate in the reverse manner.

I claim 1. A temperature compensating device for electrical apparatus adapted for minute currents, comprising: a suitable perforated container of low coefficient of expansion; a

plurality of contact disks within said container; and a member of high coeflicient of expansion within the said container, said contact disks and member being affected by the differential expansion between the same and the said container under variations in temperature of the surrounding medium to correspondingly vary the electrical resistance of said contact disks and member.

2. A temperature compensating device for electrical apparatus adapted for minute cur- 3. A temperature compensating device for,

electrical apparatus, comprising: a perforated insulating tube of low coefiicient of expansion; metallic I caps closing-the ends of the same and adjustable thereon; lock nuts to hold said caps in position; and a plurality of adjacent graphite disks and a zinc tube closed at the ends and abutting the series of disks, said disks and tube being held within said perforated insulating tube by the pressure exerted between the said metallic caps and with which they are in electrical connection.

Signed at New York, in the county of New York and State of New York this 26th day of July A. D. 1910.

WILLIAM H. BRISTOL.

Witnesses LAURA E. SMITH, FREDK F. SoHUETz. 

